With the expansion of communication networks to connect ever more people to each other and to sources of entertainment and information, and to support autonomous communication between devices that support modern technology and culture, the networks have provided an enormous increase in communication connectivity and bandwidth. The physical infrastructures that support the networks have become increasingly more complex and have developed to enable an increasing variety of communication functionalities.
To provide for a greater variety of functionalities, optical fiber interfaces have, by practical necessity, been configured in small modules that are easily mounted onto communications equipment. By using such modules, communications equipment can be easily adapted to a large variety of optical fiber physical layers, such as single-mode or multi-mode fiber; short-range (less than 1 km), long range (10 km), or extended-range (80 km) coverage; different wavelengths of light such as 850, 1310, 1490, or 1550 nm (nanometer); and single wavelength, Coarse Wavelength Division Multiplexing (CWDM), or Dense Wavelength Division Multiplexing (DWDM). Without such modules communications equipment vendors would need to manufacture a wide variety of equipment, identical in communications functionality but differing in fiber optical interface characteristics.
Modern versions of these communications modules are pluggable, i.e. they may easily be inserted into and removed from matching receptacles, referred to as “cages” mounted on panels of communications equipment, such as switches and routers. The cages serve to mechanically and electronically connect the communication modules inserted into the cages to the communications equipment.
Standards for small communication modules, such as Small Form-factor Pluggable (SFP) modules, Enhanced Small Form-factor Pluggable (SFP+) modules, 10G Form-factor Pluggable (XFP) modules, 100G Form-factor Pluggable (CFP) modules, and Gigabit Interface Converter (GBIC) modules, have been specified by industry groups in agreements known as “multisource agreements (MSA)”. Multisource agreements specify electrical, optical, and physical features of the modules. Hereinafter the acronym “SFP” may be used generically to reference small communication modules, such as any of the exemplary small communication modules noted above.
Conventional small communications modules such as SFPs are limited in functionality to performing electric to optical and optical to electric conversions. Recently, additional functionalities have been implemented inside such modules, effectively turning these modules into sophisticated network elements in their own right. For example, U.S. Pat. No. 7,317,733 to Olsson and Salemi describes performing Ethernet to TDM protocol conversion inside an SFP. US patent application 2006/0209886 to Silberman and Stein further describes pseudowire encapsulation inside an SFP. U.S. Pat. No. 7,933,518 to Li et al describes performing optical loopback and dying gasp inside an SFP. U.S. Pat. No. 7,693,178 to Wojtowicz describes inserting Passive Optical Network ONU functionality into an SFP. SFPs and similar pluggable modules with such additional functionalities save rack space, power, and cabling, but suffer from the same deficiency as communications equipment before the introduction of SFPs, namely that vendors need to manufacture a wide variety of SFPs identical in communications functionality while differing only in fiber optical interface characteristics.